the personal blog of a newly-fledged biomedical informatician, about anatomy, computers, life, or just anything she finds interesting that day

Sunday, September 30, 2007

Strata

Before my conference in Cincinnati, I visited my in-laws in Kentucky, and they drove me around to show me the state. I used to "commute" back and forth on I-65 between Birmingham, AL and Bloomington, IN, but Kentucky is such a convergence of landscapes that that experience didn't give me any inkling of what the center of the state looks like.

Much of the drive to and from Lexington goes through rock like this (not too shabby for shooting out the back seat of a moving car, is it? :) :

So I totally get the horizontal lines--that's the layers of rock that the glaciers deposited in sequence as they expanded and receded. Those horizontal layers tend to be a lot more regular than I would have thought; it's amazing how straight they can be.

It's the vertical lines that mystified me, until Dad explained. Those are the holes left by the drill bits as the builders were cutting through the hills to put in the freeway. They'd drill down at regular intervals, pack the holes full of explosives, and BOOM! I would have expected a wholesale, uncontrolled explosion, followed by a big unholy mess to clean up, but Dad explained that this technique caused the rock to shear off in vertical layers--a relatively neat and controlled process.

The explanation makes sense, certainly lots more than the vertical glaciers I was trying to imagine putting down those lines.